Videoconferencing systems allow two or more locations to communicate across duplex (i.e., simultaneous, two-way) audio and video channels. The availability of low cost, high capacity broadband services supported by powerful processors capable of sophisticated compression algorithms has led to the widespread use of videoconferencing in a wide variety of communications—personal, business, education, government, etc.
A multipoint control unit (MCU) is a device that is used to interconnect, or bridge, three or more remote clients (terminals, workstations, gateways, etc.) into one simultaneous videoconference session. among three or more remote points is possible by means of a Multipoint Control Unit (MCU). This is a bridge that interconnects calls from several sources (in a similar way to the audio conference call).
The MCU can be located at an endpoint of a local area network (LAN). The MCU can collect bandwidth capability data for each of the remote clients of a videoconference. The MCU then configures the session to meet the capability of the least powerful remote client to assure that the videoconference is of the best quality for each participant.
An MCU can be a stand-alone device or it can be embedded into dedicated videoconferencing units. At a high-level, the MCU can be viewed as including two components, a single multipoint controller (MC), and one or more multipoint processors (MP), sometimes referred to as the mixer.
The MC controls the conferencing while it is active on the signaling plane—managing conferencing creation, endpoint signaling and in-conferencing controls. The MC can negotiate parameters with every endpoint in the network and control conferencing resources. The MP(s) operate on the media plane and receive media from each endpoint, and then generates output streams from each endpoint and redirects the information to other endpoints in the conference.
Digital compression of audio and video streams in real time is performed by a coder/decoder (codec). The compressed digital stream can be subdivided into labeled packets, which are then transmitted through an electronic communication network under a known protocol.